1. Field of the Invention
The present invention relates to a polymeric fluorescent substance, a polymer light emitting device (hereinafter, referred to as polymer LED) containing the same in an light emitting layer, and a device using the same.
2. Description of the Related Art
Light-emitting materials having higher molecular weight (polymeric fluorescent substance) are variously investigated since they are soluble in a solvent and can form a light-emitting layer in a light-emitting device by an application method, differing from those having lower molecular weight. As the polymer material which can be used in a polymer LED as a light-emitting material or charge transportation material, there are conventionally known polyphenylenevinylene derivatives, polyfluorene derivatives, polyphenylene derivatives and the like. For example, Japanese Patent Application National Publication (Laid-Open) No.11-502248 has disclosed copolymers of oligophenylene. One example thereof is oligophenylenevinylene. Japanese Patent Application Laid-Open (JP-A) No. 11-246660 has disclosed copolymers of an aromatic amine compound group and an unsaturated double bond group. Specifically, a copolymer of a dimer of triphenylamine and un-substituted terphenylene is exemplified. Further, as the polymer material containing 2,5-dialkoxyphenylene, copolymers such as phenylene, thiophene, pyridine, biphenylene, bithiophene and the like have been known (Synthetic Metals, vol. 102,p. 1060 (1999)).
An object of the present invention is to provide a polymeric fluorescent substance containing a specific phenylene structure and showing strong fluorescence and/or excellent charge transporting property, and a polymer LED of high performance which can be driven at low voltage with high efficiency using this polymeric fluorescent substance.
The present inventors have intensively studied and resultantly found that a polymeric fluorescent substance showing fluorescence in the solid state and having a polystyrene reduced number-average molecular weight of 103 to 108, wherein the substance contains one or more repeating units of formula (1) and one or more repeating units of formula (2), shows strong fluorescence and/or excellent charge transporting property, and a polymer LED of high performance which can be driven at low voltage with high efficiency is obtained by using this polymeric fluorescent substance, leading to completion of the present invention.